Smart and Cost efficient Energy Interactions in Building Complexes
Smarte og kostnadseffektive
energiinteraksjoner i bygningskomplekser
Stefan Peter Erhard Schumacher
Master's Thesis
Supervisor: Trygve Magne Eikevik, EPT
Department of Energy and Process Engineering Submission date: May 2015
Norwegian University of Science and Technology
NTNU
Norwegian University Department of Energy of Science and Technology and Process Engineering
EPT-M-2014-160
*
•
MASTER THESIS
for
Student Stefan Schumacher Fall 2014
Smart and cost efficient energy interactions in building complexes Smarte og kostnadseffektive energiinteraksjoner i bygningskomplekser
Background and objective
Easy access to reliable low cost energy has been an important parameter in developing the high living standard in industrialised countries. This has resulted in a tremendous increase in energy use worldwide. Increased energy efficiency is one of the most important measures to curb greenhouse gas emissions (GHG) and secure future energy supply. IEA has come out with the general term Negawatt (Energy not used) to describe energy efficiency options. There is an extensive focus on improving energy performance of buildings and reducing the primary energy use by enforcing legislation like building legislation. This brings about a completely new set of boundary conditions for design and operation of energy interaction in buildings. Energy efficiency can also be seen as a major energy source and an opportunity for value creation.
Increased utilization of surplus heat/cool has been pinpointed by the Norwegian Energy21- report3 as an important strategic research area.
The objective of this work is to look into the different sub-systems of such an interconnected energy system for the investment and Life cycle cost point of view. The goal in future building projects, where several buildings with different functions are connected, is the utilization of surplus heat and efficient interaction between energy demand, surplus heat/cold and thermal storage in the building complexes.
The following tasks are to be considered:
1. Literature on review energy interactions in buildings, third party deliverance 2. Define a case
3. Structure the different subsystems to be connected (heat/cold supply, recovery, storage, distribution, etc) with respect to investment costs, LCC.
4. Develop a model to simulate the operation of the case buildings on an annual base comparing different subsystem options
5. Describe optimization methods
6. Make a scientific paper with main results from the thesis 7. Make proposal for further work
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Within 14 days of receiving the written text on the master thesis, the candidate shall submit a research plan for his project to the department.
When the thesis is evaluated, emphasis is put on processing of the results, and that they are presented in tabular and/or graphic form in a clear manner, and that they are analyzed carefully.
The thesis should be formulated as a research report with summary both in English and Norwegian, conclusion, literature references, table of contents etc. During the preparation of the text, the candidate should make an effort to produce a well-structured and easily readable report.
In order to ease the evaluation of the thesis, it is important that the cross-references are correct.
In the making of the report, strong emphasis should be placed on both a thorough discussion of the results and an orderly presentation.
The candidate is requested to initiate and keep close contact with his/her academic supervisor(s) throughout the working period. The candidate must follow the rules and regulations of NTNU as well as passive directions given by the Department of Energy and Process Engineering.
Risk assessment of the candidate's work shall be carried out according to the department's procedures. The risk assessment must be documented and included as part of the final report.
Events related to the candidate's work adversely affecting the health, safety or security, must be documented and included as part of the final report. If the documentation on risk assessment represents a large number of pages, the full version is to be submitted electronically to the supervisor and an excerpt is included in the report.
Pursuant to "Regulations concerning the supplementary provisions to the technology study program/Master of Science" at NTNU §20, the Department reserves the permission to utilize all the results and data for teaching and research purposes as well as in future publications.
The final report is to be submitted digitally in DAIM. An executive summary of the thesis including title, student's name, supervisor's name, year, department name, and NTNU's logo and name, shall be submitted to the department as a separate pdf file. The final report in Word and PDF format, scientific paper and all other material and documents should be given to the academic supervisor in digital format on a DVD/CD-rom or memory stick at the delivery of the project report.
^] Work to be done in lab (Water power lab, Fluids engineering lab, Thermal engineering lab)
^] Field work
Department of Energy and Process Engineering, September 16th 2014
Prof. Olav Bolland Prof Trygve M. Eikevik Department Head Academic Supervisor
e-mail: [email protected]
Research Advisor: e-mails
Dr. Armin Hafner, SINTEF Energi ajTOinJiafiiej^sintefjio
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I
Preface
This Master’s thesis was written during winter 2014 and spring 2015 as the final part of my MSc degree in Environmental Engineering at the Department of Energy and Process Engineering at the Norwegian University of Science and Technology (NTNU).
Many persons have contributed with information and helped me during the work on this Master’s Thesis and I want to thank all of them for their support. First and foremost I would like to thank my research advisor Armin Hafner from SINTEF Energi AS who gave me the chance to write the Master’s Thesis at the NTNU, for all the good advice he has given me and for always having time to discuss my questions. I would also like to thank the PhD student Daniel Rhode from NTNU and the research scientist Hanne Kauko from SINTEF Energi AS who helped me to get fast into the topic and all their support during writing the Master’s Thesis.
Further, I would like to acknowledge all people who provided me necessary data and information, all of you helped me a lot.
I would like to give a special thanks to my family for believing in me and for their financial support and my girlfriend Ingrid Dyrhaug who supported me and helped me in many different ways during this work.
Last but not least I want to thank all my fellow students and professors who accompanied me during all my studies, gave me support, inspired and motivated me.
Trondheim, May 2015.
Stefan Schumacher
II
Abstract
Efforts of the extension of new energy sources from renewable energies are motivated by the strategy of Energi21, which was published in 2014 by the Norwegian Ministry of Petroleum and Energy. The intention of this study is to fulfill the ambitions of the Energi21 strategy. The study is based on the building project in the Risvollan district of Trondheim, Norway. The building project includes a kindergarten, apartment building, assisted accommodation, care home and the existing Risvollan Center with shopping and healthcare floor.
An energy analysis based on the software program SIMIEN provides information about the expected heat and cold demand of the Risvollan buildings. Based on this energy analysis and the applicable technologies for covering the thermal energy demand of the buildings, three energy concepts are designed. Operation methods of each energy concepts are discussed and the system components are dimensioned.
Assessments of the energy efficiency of the three energy concepts are made. The energy efficiency ratios are decisive for the calculations of the expected annual costs. The Levelized Energy Costs (LEC) are made in order to compare the energy concepts from an economically point of view.
The conclusion of this study shows that all three energy concepts are able to meet the target of covering the Risvollan project buildings with sufficient thermal energy. The LEC analysis has shown that during the system lifetime of 25 years the higher investment costs of the exploitation of the renewable energy sources for producing thermal energy is advantageous compared to the purchase of external thermal energy.
III
Sammendrag
Intensjonen til denne masteroppgaven er å oppfylle ambisjonene i Energi21-strategien publisert av olje- og energidepartementet i 2014. Denne strategien tar sikte på å bruke nye fornybare energikilder i bygninger. Studien omhandler byggeprosjektet som er under planlegging på Risvollan i Trondheim. Der skal det oppføres et bygningskompleks som inkluderer barnehage, boliger, omsorgsboliger og sykehjem, i tillegg til det eksisterende Risvollansenteret som inneholder forretninger og helsesenter.
Energianalysen av det planlagte bygningskomplekset er basert på softwaren SIMIEN som estimerer varme- og kuldebehovet til bygningene. Basert på denne energianalysen og tilgjengelig teknologi som kan benyttes for å dekke behovet for termisk energi, er det utarbeidet tre energikonsepter.
Vurderinger av energieffektivitet er gjort for de tre konseptene. Energieffektiviteten er avgjørende for å beregne de forventede årlige kostnadene. Levelized Energy Costs (LEC) er brukt for å sammenligne de tre konseptene fra et økonomisk synspunkt
Konklusjonen i studiet er at alle de tre energikonseptene dekker behovet for termisk energi i bygningene. LEC-analysen viser at høye investeringskostnader for å produsere termisk energi i bygningene er fordelaktig i forhold til å kjøpe eksternt produsert termisk energi over 25 år.
IV
Content list
List of figures ... VI List of tables ... VIII Abbreviations ... IX
1 Introduction... 1
1.1 Motivation ... 1
1.2 Objectives ... 2
1.3 Content outline ... 3
2 Background theory ... 4
2.1 Thermal energy sources, storage and system components ... 4
2.1.1 Heat pump ... 4
2.1.2 Geothermal energy... 5
2.1.3 Solar thermal system ... 8
2.1.4 Ice thermal energy storage ... 10
2.1.5 District heating ... 11
2.2 Energy efficiency ... 13
2.2.1 Energy efficiency in buildings ... 13
2.2.2 Energy efficiency of thermal energy systems ... 14
2.3 Levelized Energy Costs ... 15
3 Project frame conditions ... 17
3.1 Subsurface ... 17
3.2 Buildings ... 19
3.2.1 Kindergarten and social service building ... 20
3.2.2 Apartments north ... 21
3.2.3 Assisted accommodations ... 22
3.2.4 Care home ... 23
3.2.5 Healthcare floor and shopping floor ... 25
3.3 Solar irradiation ... 26
4 Energy analysis of the Risvollan project area ... 28
4.1 Heat profile ... 29
4.1.1 Annual Heating demand ... 29
4.1.2 Specific Heating Demand ... 31
4.2 Cold profile ... 32
4.2.1 Annual cooling demand ... 32
4.2.2 Specific Cooling demand ... 33
4.3 Electrical energy demand of the buildings ... 34
4.4 Solar heat yield of the rooftop area ... 36
V
4.5 Thermal energy extraction of a geothermal well grid ... 40
5 Concepts for thermal energy supply ... 44
5.1 Energy concept 1: solar collectors and geothermal wells ... 44
5.2 Energy concept 2: seasonal ice TES and solar heat ... 49
5.3 Energy concept 3: district heating and seasonal ice TES ... 51
6 Levelized energy costs analysis ... 54
6.1 LEC of energy concept 1 ... 55
6.2 LEC of energy concept 2 ... 56
6.3 LEC of energy concept 3 ... 57
7 Discussions ... 59
7.1 Energy concepts and levelized energy costs ... 59
7.2 Data quality and uncertainty ... 61
8 Conclusions and further work ... 62
9 Publication bibliography ... 63
VI
List of figures
Figure 1: The heat pump system ... 5
Figure 2: The borehole heat exchanger system ... 6
Figure 3: Possible specific extraction values for BHE (VDI 4640) ... 7
Figure 4: Efficiency factor of solar heat collectors (Schabbach, Leibbrandt 2014) ... 9
Figure 5: A solar collector with heat storage tank ... 9
Figure 6: The ice thermal energy storage system ... 11
Figure 7: The district heating grid system ... 12
Figure 8: Clay zones of the Risvollan project area ... 18
Figure 9: Existing boreholes at Risvollan area ... 19
Figure 10: The Risvollan project area ... 20
Figure 11: Kindergarten and social service building ... 20
Figure 12: Apartments north ... 21
Figure 13: Assisted accommodations ... 22
Figure 14: Care home ... 24
Figure 15: Healthcare floor and shopping floor ... 25
Figure 16: Sunset and sunrise of Trondheim during the year (www.sunrisesunset.de 2015) 26 Figure 17: Monthly sum of irradiation in Trondheim (www.SoDa-is.com 2015) ... 27
Figure 18: The heating demand of the Risvollan project area ... 29
Figure 19: The detailed heat requirements ... 30
Figure 20: The cold demand of the Risvollan project area ... 32
Figure 21: The total thermal energy demand of the Risvollan project area ... 33
Figure 22: The electrical energy demand of the Risvollan project area ... 34
Figure 23: Total energy demand ... 35
Figure 24: Shadow map of the buildings at Risvollan project area ... 37
Figure 25: Efficiency factor of the heat absorber tubes ... 39
VII
Figure 26: The monthly solar yield of the usable rooftop area ... 40
Figure 27: Annual fluid temperatures for a geothermal well grid with 60 boreholes ... 43
Figure 28: Energy concept 1 - solar heat and geothermal wells ... 45
Figure 29: Minimum and maximum fluid temperatures ... 48
Figure 30: Energy concept 2 - Ice TES and solar heat ... 50
Figure 31: Energy concept 3 - district heating and ice TES ... 51
Figure 32: LEC during the lifetime of 25 years ... 60
VIII
List of tables
Table 1: Kindergarten and social service building ... 21
Table 2: Apartments north ... 22
Table 3: Assisted accommodations ... 23
Table 4: Care home ... 24
Table 5: Healthcare floor and shopping floor ... 26
Table 6: Maximal heat effect during the coldest day of the last ten years ... 31
Table 7: Maximal cold demand during the warmest day of the last 10 years ... 34
Table 8: Usable roof area for solar collectors of Risvollan buildings ... 38
Table 9: EED frame condition for a geothermal well grid with 60 boreholes ... 42
Table 10: Frame conditions for EED of energy concept 1 ... 46
Table 11: External energy input ... 55
Table 12: Appropriate technologies of the energy concepts ... 59
Table 13: Summery of energy concepts costs ... 60
IX
Abbreviations
BRA Bruksareal (effective area)
BTES Borehole Thermal Energy Storage COP Coefficient of Performance CTES Cold Thermal Energy Storage DH District Heating
DHW Domestic Hot Water
DIN Deutsche Industrie Norm (German industrial Standard) EED Energy Earth Designer
EER Energy Efficiency Ratio
EN European Norm
EU European Union
GHG Greenhouse Gases
GSHP Ground Source Heat Pump
HSPF Heating Season Performance Factor
ISO International Organization for Standardization LCOE Levelized Costs of Electricity
LCOH Levelized Costs of Heat LEC Levelized Energy Costs
NGU Norges geologisk undersøkelse (Norways geologic research institute) NOK Norwegian Krone (currency)
NPV Net present value
NS Norwegian Standart
NTNU Norges teknisk-naturvitenskapelige universitet (Norwegian University of Science and Technology) SEER Seasonal Energy Efficiency Ratio
SFP Specific Fan Power
SINTEF Stiftelsen for industriell og teknisk forskning
(The Foundation for Scientific and Industrial Research) SPF Season Performance Factor
TES Thermal Energy Storage
UTES Underground Thermal Energy Storage VAT Value-added tax
VDI Verein Deutscher Ingenieure (Associaction of German Engineers)
1.1 Motivation 1
1 Introduction 1.1 Motivation
In 2008, the European Union (EU) adopted an integrated energy and climate change policy, which included targets towards the year 2020 (European Commission, 2010). The targets are known as the 20-20-20-targets:
• 20% cut of GHG emissions from 1990s levels
• 20% renewable resources into the EU energy consumption mix
• 20% reduction in primary energy use with respect to projected levels
While in Germany the use of renewable energy means minimizing the use of fossil energy it is for Norway the exploitation of the new renewable energy sources. The reason are the different energy profiles of these countries. Norway for instance produces 97 % of their electric power from water power. The idea for expansion of renewable energy sources as well as raising energy efficiency are pinpointed in the national strategy “Energi21” established from the Norwegian Ministery of Petroleum and Energy.
The strategy of Energi21 stipulates ambitions to raise the energy efficiency in the building sector. In addition, the local and building-integrated renewable energy production should be encouraged. Hence shall be achieved a flexible integration of energy-efficient buildings into the energy system for covering the demand of electricity, heating and cooling. (Sverre Aam 2014)
The ambitions of the Energi21 strategy in energy systems is to develop energy systems with cost-effective, operationally efficient integration of renewable energy and to extend the energy production from renewable sources, distributed production and energy storage.
(Sverre Aam 2014)
This brings about a completely new set of boundary conditions for design and operation of energy interaction in buildings. The department of Energy at the research institution SINTEF in cooperation with the Norwegian technical University of Trondheim (NTNU) carry these challenges of research in energy efficiency and renewable energies into execution.
1.2 Objectives 2
1.2 Objectives
The purpose of this MSc study is to look at the Risvollan project area for supplying the planned complex of buildings with thermal energy for space heating, production of domestic hot water and space cooling.
A literature review has been made to investigate available and applicable technologies and to evaluate the technologies from an energy and cost efficient point of view. All available information of the project have been collected to make simulations with SIMIEN for discovering the heat and cold demand of all planned buildings based on the requirements of the Norwegian passive house standard NS 3701.
For further estimations about the extent and possibilities to provide thermal energy from a geothermal well grid and solar heat absorbers, all available information about the subsurface and solar irradiation of the project area have been collected and assembled.
In the energy analysis of the buildings at the Risvollan project area calculations for an estimation of the extent and feasibility of the available technologies have been made. All calculations and estimations are based on the SIMIEN calculations for the thermal energy demand. The required size of a geothermal well grid has been simulated with the computer software “Energy Earth Designer (EED)”. The usable rooftop area for solar heat absorbers has been determined under the consideration of unusable shadow area and the efficiency factors of the absorbers.
Three energy concepts are designed for covering the thermal energy demand of the buildings in the Risvollan project area. The concepts are based on the considered technologies and their calculations for dimensioning. The three energy concepts includes a geothermal well grid, solar heat absorbers, an ice TES and the supply from the district heating grid. For evaluating the expected energy efficiency there are made predictions about the system ratios for heating and cooling. The calculation of the dimensions of the system components are made and are the basic data for the Levelized energy cost analysis (LEC) for the lifetime of 25 years for heating systems.
1.3 Content outline 3 The calculated LEC of the three energy concepts are compared and evaluated for an economically assessment.
1.3 Content outline
The whole study is divided in 9 chapters. Chapter 1 is the introduction that covers the motivation of the study, objectives of the study and the content outlines.
Chapter 2 of this Master’s Thesis includes the literature review. The sources and components of thermal energy production are considered as well as frame conditions and evaluation methods of energy and cost efficiency.
In chapter 3, all frame conditions and available information of the Risvollan project are collected and assembled. The consideration of the project includes the conditions of the subsurface, available information about the planned Risvollan project area, details about the planned buildings and data about the expected solar irradiation in Trondheim.
Simulations with the software SIMIEN for the expected heat and cold demand of the Risvollan buildings are made in in chapter 4. An analysis of the energy availability from the thermal energy sources are made. The analysis includes calculations about the solar yield of the roof top area and a simulation with the computer software Energy Earth Designer (EED) for figuring out the underground conditions for a geothermal well grid.
Three possible concept variants for supplying the Risvollan project buildings with thermal energy during the changing annual demand are designed in Chapter 5. The concepts include all mentioned thermal energy sources and system components from chapter 2. All concept components are dimensioned as accurate as possible based on the available information.
In chapter 6 the LEC of each concept is calculated. Frame conditions are explained and all available cost and price information is included.
A final discussion of all concepts and results including a consideration of the data quality is made in chapter 7. The summery of the entire study as well as recommendation for further work is covered in the chapter 8. The final chapter 9 includes the Publication bibliography.
2.1 Thermal energy sources, storage and system
components 4
2 Background theory
2.1 Thermal energy sources, storage and system components
Thermal energy in the building sector is mainly used for heating, cooling and the production of domestic hot water. The annual thermal energy demand varies seasonally. In northern Europe the heat demand decreases considerably during winter while cold energy during the summer month is needed. However, heat energy offered by the sun is mainly available during the summer, while cold energy is climate-related rather disposable during the winter months.
A smart energy system closes the gap of that mismatch.
Thermal energy storage (TES) is one of the key technologies for energy conservation and therefore, it is of great practical importance. One of its main advantages is that it is best suited for heating and cooling thermal applications. (Dinçer, Rosen 2011)
For designing suitable energy concepts, it is important to find applicable thermal energy sources and storage system for the considered Risvollan project area. Theoretical applicable thermal energy sources and storage systems are considered in the following chapters.
2.1.1 Heat pump
The first impulse for using heat pumps has been delivered by the need of cooling food in order to increase its storage life during transportation. Nowadays heat pumps are used for heating as well as cooling tasks in a bright range of application. (Banks 2012)
By applying technical work to the heat pump, it moves heat energy from a low temperature level to a level at higher temperature. (Huggins 2010) An amount of external power (approx.
25 %), mostly electrical energy, is used to accomplish the energy transformation from the heat source to the heat sink. The heat pump cycle is a closed system and consists of two heat exchangers, the condenser and the evaporator, an expansions valve and a compressor. A refrigerant circulates inside the so-called vapor-compression-cycle. A heat pump cycle with all components is shown in Figure 1.
The refrigerant flows from the compressor through the condenser and changes the status from gaseous into liquid while giving off the heat to the heating system. After the condenser,
2.1 Thermal energy sources, storage and system
components 5
the refrigerant passes the expansion valve where it cools down and transforms partially from liquid into vapor. The refrigerant flows through the evaporator, absorbs heat from the heat source, and evaporates completely.
Figure 1: The heat pump system
Now, the refrigerant is compressed from a low-pressure to a high-pressure gaseous state.
During compression, the refrigerant is heated again.
A reversible type of a heat pump is able to reverse the cycles flow. Than the evaporator and the condenser switch its function and the system can be used for cooling. Thus, a reversible type can be used to provide heat in the winter and cold in the summer.
2.1.2 Geothermal energy
Humans have been using geothermal Energy for several 1000 year. In 1791 Alexander von Humboldt ascertained that the temperature increase by the geothermal gradient of 3,8°C per 100 m depth in Freiberg’s mining area. (Stober, Bucher 2014)
2.1 Thermal energy sources, storage and system
components 6
Geothermal energy is the stored energy in the form of heat beneath the surface of solid earth.
(Banks 2012) Nowadays, a common technique to use geothermal energy is the extraction of heat from boreholes. A distinction is made between the shallow geothermic up to 400 m and deep geothermic from 400 m until over 1,000 m. (Stober, Bucher 2014)
In order to use the heat from shallow geothermal wells for space heating in buildings it is necessary to extract the heating energy of the underground by heat pumps. Various shallow geothermal system like geothermal collectors (horizontal loops), borehole heat exchanger (vertical loop), energy piles, and groundwater wells can be used to extract and/or store heat from the underground (Stober, Bucher 2014). A BHE system with vertical loop is shown in Figure 2.
Figure 2: The borehole heat exchanger system
A borehole heat exchanger (BHE) is a system consisting of tubes, which are installed, in a borehole and in which a heat transfer fluid circulates. Types of tube systems are single-U, double-U, triple-U and coaxial tubes. The usually used type is the double-U tube. (Stober, Bucher 2014)
The BHE receives heat supply from the borehole’s surrounding and depends on the thermal conductivity of the underground. The individual thermic conductivity of a boreholes
2.1 Thermal energy sources, storage and system
components 7
surrounding can be measured by the standard method called Thermal Response Test. The length of a borehole depends mainly on the necessary heat demand and the thermal properties of the underground (Stober, Bucher 2014). Preliminary research results have confirmed that the thermal conductivity of the rock mass and grout have the greatest impact on the efficiency of underground thermal energy storage (Wołoszyn, Gołaś 2014). A recommendation about the specific heat extraction from different underground types are listet from VDI 4640 for 1,800 h and 2,400 h operation time during one year and is shown in Figure 3.
Figure 3: Possible specific extraction values for BHE (VDI 4640)
Boreholes can also be used as Thermal Energy Storage (BTES). In summer season surplus heat can be injected into the underground. The underground regenerates thermally from the winter extraction and additional heat can be stored there too. However, a single borehole is efficient for neither inter-seasonal nor day/night underground thermal energy storage. BHE- fields are a system of minimum five connected BHE. BHE-fields are mostly used for seasonal heat storage but also in order to cover the cooling demand of buildings. It is recommended to maintain a constant distance around 5 m between the boreholes and the upper surface of the heat store must be thermally insulated to reduce heat losses to the atmosphere. One of the
2.1 Thermal energy sources, storage and system
components 8
Europe’s biggest BHE-fields is the plant of Lørenskog of the Ny Ahus hospital in Norway. It consist of 350 BHE, each of them are 200 m deep.(Stober, Bucher 2014; Lanini et al. 2014)
2.1.3 Solar thermal system
Using solar thermal energy has a long tradition in the humankind’s history. Nowadays, solar heat application in small scale for warm water production for instance, but also huge solar heating power plants exist. (Schabbach, Leibbrandt 2014)
The absorbing material of the solar collector absorbs the radiation energy of the sun. As a result the material’s temperature increase. (Schabbach, Leibbrandt 2014) Different types of collectors such as simple heat absorber tubes, flat-plate collectors or evacuated-tube collectors are used.
The absorber of a solar collector absorbs the radiation energy of the sun and heats the through the absorber flowing liquid, mostly water with added antifreezer. Afterward the liquid flows to a facility where the heat is used directly or to a heat storage tank. (Robert Stieglitz, Volker Heinzel 2012). A simple variant of the combination of heat storage tank and solar collector is shown in Figure 5.
Even with the best alignment of the sun collectors, the maximum efficiency of 70 up to 80 % for transforming the solar irradiation into heat can be reached. Under consideration of the system temperatures and the type of the collector, the efficiency is even smaller. (Schabbach, Leibbrandt 2014)
2.1 Thermal energy sources, storage and system
components 9
Figure 4: Efficiency factor of solar heat collectors (Schabbach, Leibbrandt 2014)
As it is shown in Figure 4, the efficiency of the different kinds of sun collectors highly depending on the difference between average fluid temperature and the surrounding temperature.
Figure 5: A solar collector with heat storage tank
2.1 Thermal energy sources, storage and system
components 10
The incoming radiation depends on the general atmospherically influences, the geographical location, date, time of the day and especially of the clouds. The yield of a solar plant depends mainly on the collector’s area and storage dimension. In the buildings sector solar plants are mainly used for heating tap water and supporting the space heating system. (Schabbach, Leibbrandt 2014) In combination with geothermal wells, the solar energy can be used to regenerate boreholes thermally.
2.1.4 Ice thermal energy storage
The oldest example of an ice thermal energy storage (CTES) is to harvest ice from lakes and rivers and storing it in a well-insulated warehouse for using it for preserving food, cooling drinks, and air conditioning. (Dinçer, Rosen 2011)
Thermal energy storage (TES) means conserving of energy for later use. If a material releases or absorbs heat energy while the temperature of the material increases or reduces, than it is sensible heat and can be calculated by the first law of thermodynamic:
= ∙ ∙ ( − )
If the heat storage material involves phase transitions during absorbing or releasing energy, than the energy used for the transition is called latent heat. The required energy to convert ice to water is called heat of fusion. The phase changing process during absorbing or releasing latent heat happens without changing the materials temperature. (Dinçer, Rosen 2011;
Huggins 2010)
An ice TES is a water filled storage tank. Depending on the operation method, the ice TES can be used as heat or cold supplier. In case of the utilization as a heat supplier, a medium, mostly brine or refrigerant, flows through the heat exchanger coils inside the tank. The heat energy is transferred between the water inside the tank and the fluid in the coils. During the discharging mode, the water in the tank cools and the phase transition of the water into ice occurs. In the charging mode, heat energy is led into the tank, the solid ice melts and the temperature inside the tank increases. (Kalaiselvam, Parameshwaran). An ice TES system during supplying cold energy to a heat exchanger is shown in Figure 6.
2.1 Thermal energy sources, storage and system
components 11
Figure 6: The ice thermal energy storage system
The cooling capacity of an ice TES system under total freezing is 18 times higher than that of a water CTES operating between 12 and 7°C. Ice TES systems require less space than water CTES systems because of the higher energy storage capacity during freezing.
∶ 7°C Water (1kg)())* 12°C Water (1kg) = 20.9 kJ#,% &'
01 ∶ 0°C Ice (1kg)445,5 &'()))* 0°C Water(1kg)6#, &'())* 12°C Water (1kg)= 384,6 kJ
A CTES system has a high potential for increasing the efficiency of the seasonal use of thermal energy referred to the mismatch between the supply and demand of thermal energy in buildings. The period of storage can vary from a few hours for diurnal storage cycles, to many months for seasonal (annual) cycles. A thermal applications of a CTES is cooling and air- conditioning but also space heating or supply of hot water. (Dinçer, Rosen 2011)
2.1.5 District heating
The district heating system distributes thermal energy, which is produced in a central location to a costumer unit where it can be used for heating requirements such as space heating or domestic warm water production. Energy sources for generating district heat can be manifold.
2.1 Thermal energy sources, storage and system
components 12
The most common sources are waste, biofuel, heat pumps, landfill gas, natural gas, propane/butane gas, electricity and fuel oil. A network provides the generated heat to the costumer. The main distribution network consists of two insulated pipes, the supply and return lines. The forward water to the costumer provides temperatures between 80°C and 120°C and the return water lines reaches temperatures from 45°C to 75°C. The heat between customer and the providing networks is usually provided by a heat exchanger. An example of a DH-grid is shown in Figure 7. A typical average of the heat losses of the providing network is around ten percent. Higher efficiency and better pollution control can be reached of district heating plants instead of localized small-scale production systems. (Statkraft 2009)
Figure 7: The district heating grid system
The heat energy for the district heating network of Trondheim is produced of nearly 70 % out of municipal solid waste. Every year the plant burns more than 200,000 tons of waste. The burnt waste comes from the entire Central Norway region, from Saltfjellet in the north to Dovre in the south. The other 30 % of the heat production is supplied by the use of bioenergy, heat pumps, gas, electricity and small amounts of oil .The plant produces 600 GWh heat a year. The entire network consists of 10 heating plants and 250 km distribution grid (Statkraft 2009)
2.2 Energy efficiency 13
2.2 Energy efficiency
Effectivity and Efficiency is closely related but it must be differentiated between these terms.
While Effectivity is the proportion of reaching a defined target under input of all means, means Efficiency meet the target with a minimum of means. In everyday speech, it can be expressed in the following words: “Effectivity is to do the right things and efficiency is to do the right things right.” (Pehnt 2010)
In the view of heat energy supply of buildings, two subsystems must be considered. On the one hand, the building consumed energy must be minimized and on the other hand, the heating system itself should run as efficient as possible. Both systems together is to understand as a total-system Building+Heating. The main aim of this system is to fulfill the comfort requirements of the user and residents. (Pehnt 2010) Heat isolation and the reuse of heat losses of buildings but also the exploitation of all heat and cold sources as well as an elaborated energy management system are necessary to fulfill the energy effectivity and efficiency of the total system.
2.2.1 Energy efficiency in buildings
The actual construction regulation (Byggteknisk forskrift) is called TEK10. The new regulation TEK15, is expected to come into force in 2015. It is expected that the requirements for new planed and constructed buildings are orientated on the passive house standard NS 3701:2012.
The actual methods and data for calculating the energy performance of buildings to meet the requirements of the TEK10 are included into the standard NS 3031. The NS 3031 includes residual buildings as well as public building types. In addition, the operation times of the different build types are included here. These times deliver information to control the heat and cold behavior between the operation times.
The passive house standard NS 3701 contains criteria for heat losses of transmission and infiltration, but also benefits from solar and internal loads are included. The building must be designed to have an annual heating demand of not more than 15 kWh/m2 and a cooling demand of 15 kWh/m2 or with a peak heat load of 10 W/m2. The total primary energy consumption (heating, hot water and electricity) must not be more than 120 kWh/m2 per year
2.2 Energy efficiency 14 and the air leakage value of the building must not be higher than 0.6 times the house volume per hour (n50 ≤ 0.6/h) at 50 Pa. The NS 3701 is valid for public buildings. (Passivhaus Institut)
2.2.2 Energy efficiency of thermal energy systems
A thermal energy system is often a very individual system, which includes different components and energy sources. Every system varies in size, components, requirements, operation methods, geographical and climatically circumstances. Energy efficiency of such a system can be measured for single components as well as for the total energy system. A consideration of the energy efficiency can be done for a fix point of time and a period. The most important parameters for an evaluation of energy efficiency are the heat output and the electrical energy input.
A heat pump is the most significant device of a thermal system. A reversible type is used for cooling and heating tasks. It is common to measure the COP to rate heat pump efficiency in a heating circulation system. The higher the COP is the more efficient runs a heat pump. The COP represents the efficiency to a fix point of time and shows the rate of heat output to the electrical energy input. (Stober, Bucher 2014; Wosnitza 2012)
COP = Heat Output Electrical Energy Input
During the year, outdoor temperatures are changing and accordingly the necessary heat requirements varies. For evaluating the efficiency of an entire heating system during a period of time, the Seasonal Performance Factor (SPF) can be used. The SPF includes the additional electrical energy demand of the equipment that is used to run the heating cycle. The higher the SPF is the more efficient runs heating system. (Kanoglu et al. 2012).
SPF = Total Seasonal Heating Output Total Electrical Energy Input
The Energy Efficiency Ratio EER is used to evaluate a heat pump’s efficiency in the cooling cycle. Like the COP, the EER shows the efficiency of a fixed point of time. (Kanoglu et al. 2012)
EER = Cooling Capacity Electrical Energy Input
2.3 Levelized Energy Costs 15 The Seasonal Energy Efficiency Ratio rates the seasonal cooling performance for the cooling cycle. Additional energy demand of the equipment for the cooling cycle is included. The higher the SEER, the more efficiently the heat pump cools. (Kanoglu et al. 2012)
SEER = Total Seasonal Cooling Output Total Electrical Energy Input
2.3 Levelized Energy Costs
Levelized Energy Cost (LEC) are also known as the Levelized Cost of Electricity (LCOE). LEC is a convenient tool for comparing the energy unit costs of different technologies over the economic life of the energy system. The LEC method, is used as a benchmarking tool to assess the cost-effectiveness of different energy generation technologies (IEA - International Energy Agency 2010).
The LEC includes all costs of the analyzed energy system over the system’s lifetime. The calculation includes the initial investment costs, operations and maintenance costs, cost of fuel and the cost of capital. The LEC is defined as the total lifetime cost of an investment divided by the cumulated generated energy by this investment (Pawel 2014). The equation of the LEC is defined as follow: (Hernández-Moro, Martínez-Duart 2013)
KLM = N∑ MPQRQ
S1 + U
SVSW#
X
N∑ L
S1 + U
SVSW#
X
The costs consists of the Investment expenditures in year n, operations and maintenance expenditures in year n and the Fuel expenditures in year n. En is the energy generation in year n, r is the discount rate and N is the lifetime of the system. The summation starts with n=0. If the entire initial costs for building the energy system are invested once at the beginning of the first year, than the initial costs can be excluded of the running costs. In that case the calculation starts with n=1 (Hernández-Moro, Martínez-Duart 2013).
2.3 Levelized Energy Costs 16
KLM = NYZ[R[\] MPQRQ + ∑ ^ZZ_\] MPQRQ
S(1 + U
SVSW#
X
∑ L
S1 + U
SVSW#
The calculation method of the discount rate r depends on the financing method. In case of financing with outside borrowed capital it must be calculated like in the following equation:
(David Keeping, Sintef 2007)
U
`= 1
1 + a ∙ b U
S1 − Q − [ 1 + [ − ac
i means the inflation, s the tax rate, e is for rate of price increase and rn stands for the nominal interest rate. In case of self-financing, the tax rate falls away and the equation can be shortened to: (David Keeping, Sintef 2007)
U
d= 1
1 + a ∙ e U
S− [ 1 + [ − af
A typically LCE is calculated over 20 to 40 year lifetime. The unit of LEC is given in the country specific currency per kilowatt-hour, for example EUR/kWh, Kr/kWh or $/kWh. LEC studies are very individual and are highly dependent on the different sources of the information. The quality and validity are dependent on the assumptions, financing terms and the analyzed technological deployment. For a comparison of the LECs for different systems, it is very important to define the systems boundaries. (IEA - International Energy Agency 2010)
An alternative but mathematically identical approach is the calculation method of the net present value (NPV). The LEC is the average internal price at which the energy is to be sold in order to achieve a zero NPV. (Pawel 2014)
3.1 Subsurface 17
3 Project frame conditions
The contents of chapter three are the conditions of the subsurface, the solar irradiation and the available data for the planned buildings in the Risvollan project area. The considerations are the basic information for simulating the heating and cooling demand of the buildings in the Risvollan project area, for dimensioning the geothermal well grid, the solar heating system and the ice TES.
3.1 Subsurface
The district of Risvollan in Trondheim is situated in the south of the city, 5 km southwards from the city center. The area of Risvollan is mainly used as a residential area and the biggest housing cooperative of Norway is located here.
Multiconsult AS, Rambøll Norge AS and the Trondheim municipality did a geotechnical investigation about the Risvollan Center area in 2008 and 2013. The project area lies between 125 – 130 m above the sea-level. The terrain falls from north, west and south but rises slightly to northeast. The Risvollan project area is located between two quick clay zones, which are called Risvollan and Blakli Kvikkleiresone. The map of the quick clay zones is shown in Figure 8. The Risvollan Kvikkleiresone located north of the project area, shows a 2-3 m thick crust of clay. Beneath the topmost crust of clay fellows a tighter clay layer. (Trondheim Kommune 2013)
The upper layer consists of different kinds of clay before the bedrock starts. The bedrock, which consists of green stone and greenschist includes layer of quartzite. Green stone and greenschist are a basic magmatit (Norges geologiske undersøkelse (NGU)). The deepest test drilling “MU2_1” is located in the southeast of the Risvollan project area. The depth of this drilling is approximately 51 m deep. The location of the test drilling MU2_1 is shown in Figure 8. During test drilling of MU2_1, they have not reached the bedrock layer. (Trondheim Kommune 2013)
3.1 Subsurface 18
Figure 8: Clay zones of the Risvollan project area
Special cases are needed for drilling a well during the top layer of clay before it comes into the bedrock where the rock stabilizes the well itself. The drilling work through the clay layer is more expensive than drilling in the bedrock because of the steel cases.
The already existing boreholes around the Risvollan area are shown in Figure 9 and are marked with blue points. The map and the available data about the boreholes are provided from NGU (Norges geologiske undersøkelse). The depth from the surface to the rockbed of these boreholes is varying between 0.5 m and 84 m irregular, so that it is not possible to make a useful prediction about the expected depth to the rockbed in the project area.
In chapter 6, will be used the maximal reached depth of 51 m during test drilling MU2_1 as reference value for the thickness of the clay layer.
MU2_1
3.2 Buildings 19
Figure 9: Existing boreholes at Risvollan area
3.2 Buildings
The buildings of the Risvollan project are planned in the area between the streets
“Blaklivegen” and “Utleiervegen” of Trondheim. The plans consisting a kindergarten in the northeast, care homes in the east, the assisted accommodations in the south and a residential building in the northwest. The existing Risvollan center includes a shopping and healthcare floor and is going to be modified. The four apartment’s in the middle of the construction plan are optional and their construction depending on the future freehold conditions.
Project area
3.2 Buildings 20
Figure 10: The Risvollan project area
3.2.1 Kindergarten and social service building
The kindergarten located in northeast of the areal provides 1,000 m2 living space on two floors and is shown in Figure 11. The social service building of the Risvollan housing cooperative is connected with the kindergarten and offers a 400 m2 space.
Figure 11: Kindergarten and social service building
3.2 Buildings 21 The operation time of the kindergarten is ten hours a day and 5 days a week. The whole facade of the building consist of 20 % windows and additional 15 m2 doors. More details about the kindergarten and social service building are shown in Table 1.
Table 1: Kindergarten and social service building
Kindergarten and social service building
Effective area
(BRA) 1,400 m2 1,000 m2 Kindergarten, 400 m2 social service Facade area 1,088 m2 Thereof 15 m2 doors
Window area 20% 120 windows (each 1.60 m x 1.20 m) Heating volume 4,760 m3
Number of floors 2 Floor level: 3.4 m
Roof 700 m2 Flat roof
Ground 700 m2 Ground floor to soil
3.2.2 Apartments north
The apartments building is located in the north of the area. Three floors with 18 apartments provide a total living area of 1,620 m2 and is shown in Figure 12.
Figure 12: Apartments north
3.2 Buildings 22 Each apartment offers a living space of 60-80 m2. The facade consist of 20 % windows and 41 m2 entrance doors as well as doors to balcony and terrace. The ground floor is connected with the soil. More details of the apartment building are shown in the Table 2.
Table 2: Apartments north
Apartments north
Effective area
(BRA) 1,620 m2 6 Apartments
Facade area 1,173.6 m2 Thereof 41 m2 doors
Window area 20% 142 windows (each 1.60 m x 1.20 m) Heating volume 4,212 m3
Number of floors 3 Floor level: 2.6 m
Roof 540 m2 Flat roof
Ground 540 m2 Ground floor to soil
3.2.3 Assisted accommodations
The assisted accommodations are located in the southwest of the area and is shown in Figure 13. The building is connected to the existing Risvollan Center in the west and to Blaklivegen in the south.
Figure 13: Assisted accommodations
3.2 Buildings 23 The building has three floors with 51 accommodations. Each accommodation have two rooms with a total effective area of 55 m2 living space. Additionally there is a common room at each floor. The whole building is connected with an air-conditioned corridor. The corridors facade consist of 60 % windows. The other facades cover 20 % windows and 147.5 m2 entrance doors as well as doors to balcony and terrace. The building can also be reached from the underground parking by an elevator or staircase. All further available details are listed in Table 3.
Table 3: Assisted accommodations
Assisted accommodations
Effective area
(BRA) 4,710 m2 51 Apartments
Facade area 3904.4 m2 Thereof 147.5 m2 doors Window area 20%/60% Corridor 60%, 934 windows
( each 1.60 m x 1.20 m) Heating volume 12,246 m3
Number of floors 3 Floor level: 2.6 m
Roof 1,570 m2 Flat roof
Ground 1,570 m2 Ground floor to underground parking
3.2.4 Care home
The care home is located in southeast of the Risvollan project area. The building is accessible through the main entrance in the first floor but also from the second floor. The bedroom floors are from the second up to the firth floor. The whole care home is with three departments on each floor organized. Each department has eight rooms. All floors are identical. All together, there are 72 bedrooms. The care home is shown in Figure 14.
3.2 Buildings 24
Figure 14: Care home
Each floor of the three departments are connected with a common room. The useful area of the care center is 5,670 m2. The facade is covered with 20 % windows and additional 40 m2 doors. The first floor is accessible from the underground parking, which is connected with the parking of the Risvollan center and covers 1,080 m2 of the ground floor of the building. The other 900 m2 of the buildings underground is connected to the soil. Further details are listed in Table 4.
Table 4: Care home
Care home
Effective area
(BRA) 5,670 m2 72 rooms
Facade area 2,121.6 m2 thereof 40 m2 doors
Window area 20% 284 windows (each 1.60 m x 1.20 m) Heating volume 14,742 m3
Number of floors 4 Floor level: 2.6 m, first floor: reception
Roof 1,890 m2 Flat roof
Ground 1,980 m2 900 m2 Ground floor to soil
1,080 m2 Ground floor to underground parking
3.2 Buildings 25
3.2.5 Healthcare floor and shopping floor
The already existing Risvollan center is located in the south of the area and is shown in Figure 15. The first floor is assigned as shopping floor and the second as healthcare floor with different healthcare possibilities.
Figure 15: Healthcare floor and shopping floor
The ground is sloping at this part of the areal so that there is an entrance from the west to the second floor and another one from the east to the first floor. The south of the building is connected to the assisted accommodations. The western facade of the first floor is connected to the soil because of the sloping terrain. The rest of the facade is covered by 20 % of windows and additional 15 m2 of doors. All further details of the building are shown in Table 5.
3.3 Solar irradiation 26
Table 5: Healthcare floor and shopping floor
Healthcare floor and shopping floor
Effective area
(BRA) 4,736 m2 2 floors
Facade area 1,286.4 m2 Thereof 15 m2 doors and 321.6 m2 contact to soil Window area 20% 964.8 m2 with 114 windows
(each 1.60 m x 1.20 m) Heating volume 14,208 m3
Number of floors 2 Floor level: 2.6 m, first floor shopping, second floor health care
Roof 2,000 m2 Flat roof, 368 m2 contact to apartments tower
Ground 1,980 m2 Ground floor to soil
3.3 Solar irradiation
During a year, the intensity of the sun as well as the hours of sunlight varies. As Norway is located up north at the globe, there is a considerable difference between sunshine hours in winter and summer. In Trondheim is the time between sunrise and sunset at the maximum in June of 20h 48min and at the minimum of 4h 39min in December as shown in Figure 16.
Figure 16: Sunset and sunrise of Trondheim during the year (www.sunrisesunset.de 2015)
3.3 Solar irradiation 27 The solar energy service www.SoDa-is.com provides the monthly sum of irradiation (Imonth) in Trondheim (Figure 17). These data are used for the calculation in chapter 4.4 for the yield of the solar heat in the Risvollan area.
Figure 17: Monthly sum of irradiation in Trondheim (www.SoDa-is.com 2015) 0
21 43
99
138 142 136
103
50 24
0 0
0 20 40 60 80 100 120 140 160
1 2 3 4 5 6 7 8 9 10 11 12
Irradiation [kWh/m²]
Month
Monthly sum of irradiation in Trondheim
(mean of 2000-2005)
4 Energy analysis of the Risvollan project area 28
4 Energy analysis of the Risvollan project area
The software SIMIEN is used to simulate the energy demand, the effective use and the room climate inside the planned buildings of the Risvollan project area. SIMIEN is a Norwegian Software from the company “ProgramByggerne”. The Software is used for evaluation of building regulations, identification of energy sources, calculation of energy demand, validation of the inside climate and dimensioning of the heating system, ventilation system and air- condition. (Dokka 2014)
The TEK 15 with the new technical building regulation is expected in 2015. The new version includes regulations to reduce the energy demand of new-planed buildings. The TEK 15 shall include values for ventilation, heating and construction material properties close to the NS 3701 Passive House Standard.
The values of the Norwegian Passive House Standard NS 3701 and the Standard NS 3031 for calculating the energy performance of buildings are used as database for the SIMIEN simulations in this chapter. Input data for the SIMIEN simulation like U-values, necessary quantity of air, values for thermal bridges, air leakage rate (n50), SFP-Factor, heat input of lighting, technical equipment and persons and operation times are taken from NS 3701. The values for calculating the energy demand for heating the domestic hot water and the set point temperatures inside and outside the opening and operational hours of the buildings are taken from NS 3031.
The heat and cold demand is covered by direct and indirect energy sources. Direct energy sources is for example a geothermal energy system with heat pumps, sun-collectors or ice storage system. Internal loads from the use of lightning, electrical equipment and persons who stay inside the building are indirect energy sources. The buildings internal heat exchangers are radiators and there are additional heat exchangers placed in the ventilation system of the building. In case of the need for cooling the buildings, there is another heat exchanger located in the ventilation system for cooling.
Results of the SIMIEN simulations for the building of the Risvollan project area are depicted with Microsoft Office Excel. The original data sheets from the results of the SIMIEN simulation f each building are shown in Appendix A
4.1 Heat profile 29
4.1 Heat profile
4.1.1 Annual Heating demand
The heat demand of all buildings varies during the season. During the winter months, there is a generally higher heat supply required than in the summer months. By comparison all buildings of the Risvollan project area, the assisted accommodations show the highest heat requirement during the winter season.
Figure 18 shows the monthly heat demand of every building during a year. The main heat consumers especially between October and April, cause of the lower outdoor temperatures, are the assisted accommodations, the care home and the healthcare floor of the Risvollan Center.
At every floor of the assisted accommodation, the rooms are connected with a heated corridor whose facade have a huge window area. Standard external walls would provide better heat insulation than a facade of windows, but will not give the same lighting conditions.
Figure 18: The heating demand of the Risvollan project area 0
20 40 60 80 100 120 140
Jan Feb Mar Apr Mai Jun Jul Aug Sep Okt Nov Des
Heating demand [MWh]
Heat demand
Kindergarten Apartments north Assisted accommondations
Care home Healthcare floor Shopping floor
4.1 Heat profile 30 For SIMIEN taken values for the electrical equipment of the shopping floor differ from the generally given data from NS 3701. The reason is that reports and studies like these from Trond Ivan Bøhn (2011), Langseth (2014) and also internal experience from SINTEF have shown that shopping centers have a higher energy demand than the given values by NS 3701.
Experience of SINTEF has also shown that the internal loads by electrical utilities in a shopping center cover the required heating demand during winter.
Under consideration of this information, the values for internal loads are increased to 25 W/m2 for lighting and 55 W/m2 for technical equipment instead of the given 15 W/m2 and 1 W/m2 from NS 3031. The direct heat load of the shopping floor is after these corrections nearly constant over the year. The higher internal loads by electrical utilities are led that the heat supply with radiators and ventilation heat exchanger is smaller than 1 MWh/a. The entire heat demand of the shopping floor shown in
Figure 18 between the month February and December is required for the production of DHW.
Figure 19: The detailed heat requirements
28 25 27 27 26 26 26 26 26 27 27 27
50 45 43
23
11 2 1 1 6
26
39 50
39
26 16
2 1
9
22 38
0 20 40 60 80 100 120 140
Jan Feb Mar Apr Mai Jun Jul Aug Sep Okt Nov Des
Energy demand [MWh]
Detailed Heat Demand
Domestic hot water Ventilation heat space heating
4.1 Heat profile 31 shows the detailed monthly heat demand of DHW, heat demand of ventilation system and space heating of all buildings in the Risvollan project area. The heat load required for the DHW production is nearly constant during the year and varies between 25 and 28 MWh monthly.
The heat demand used for space heating and heating by the ventilation system varies strongly each month and depends on the prevailing outdoor temperature. During December and January the total heat demand is the highest with 117 MWh in December and 115 MWh in January. The yearly heat demand for space heating from ventilation and radiators and the supply of hot water for all buildings of the Risvollan project area is 769 MWh.
4.1.2 Specific Heating Demand
A special winter simulation with SIMIEN shows the maximal heat demand during the coldest period of the year. As reference for the winter simulation, the coldest day of the last ten years is chosen which is the 13th of January 2014. The highest temperature at the 13th of January 2014 was - 8.2°C and the lowest was -16.4°C. The average temperature this day was - 10.6°C.
The results of the simulation are shown in Table 6.
Table 6: Maximal heat effect during the coldest day of the last ten years
Winter BRA Maximal heat effect
[m2] [kW]
Kindergarten 1,400 11
Appartments north 1,620 2
Assisted accommodations 4,710 42
Care home 5,670 47
Healthcare floor 2,368 71
Shopping floor 2,368 71
Total 18,136 244
At the peak of heating during the coldest period of winter is a heating system necessary, which covers a maximal heat effect of 244 kW, for providing all buildings with sufficient heat energy.
The highest heating power is needed at the shopping and healthcare floor with 71 kW each floor. These two floors have high voluminous rooms without separation of indoor walls.
4.2 Cold profile 32
4.2 Cold profile
4.2.1 Annual cooling demand
In the high summer season from June to August, it is necessary to lower the room temperature for keeping a comfortable indoor climate. During all other months there is no need for cooling the inside climate of the buildings. Due to Figure 20 is the highest cooling load required in August, the warmest month of Trondheim. During this month, all buildings except the apartments in the north, depending on cooling down the indoor temperatures for reaching a comfortable room temperature like given in NS 3031.
The results of the SIMIEN simulation are shown in Figure 20. The cooling demand during the summer from the shopping floor in the building of the Risvollan center is the highest in comparison with the other buildings. The constantly working electrical equipment of the shopping floor delivers extra input heat during the month of summer. Cooling of the buildings during the summer season is important for preventing an increase of the temperatures above the comfortable indoor conditions. Currently, the shopping floor supplies itself with cooling energy and at the actual project status it is not given, that they will join the future energy concept.
Figure 20: The cold demand of the Risvollan project area -6
-5 -4 -3 -2 -1 0
Jan Feb Mar Apr Mai Jun Jul Aug Sep Okt Nov Des
Heating demand [MWh]
Cold demand
Kindergarten Apartments north Assisted accommondations
Care home Healthcare floor Shopping floor
